Many process control systems use pressure regulators to control the pressure of a process fluid. Pressure reducing regulators are commonly used to receive a relatively high pressure fluid and output a relatively lower regulated output fluid pressure. In this manner, despite the pressure drop across the regulator, a pressure reducing regulator can provide a relatively constant output fluid pressure for a wide range of output loads (i.e., flow requirements, capacity, etc.).
A temperature-controlled pressure regulator typically reduces the pressure of process fluid between an inlet and an outlet of the pressure regulator while controlling the temperature of the process fluid (e.g., maintaining the temperature of the process fluid at a predetermined temperature). Controlling the temperature of the process fluid prevents condensation and/or induces vaporization of the process fluid across the regulator as the pressure of the process fluid is reduced between an inlet and an outlet of the regulator.
In general, temperature-controlled regulators provide vapor pressure control and are often used with sampling systems in which analysis equipment may require the process fluid to be in a gaseous or vapor state while having a relatively low pressure. For example, in the petrochemical industry, samples of process fluid containing liquid hydrocarbons are often analyzed (e.g., via chromatographic analysis) for quality control. Such process fluid samples must often be in a gaseous state or vapor phase. Thus, a temperature-controlled pressure regulator may be used to preheat liquids, prevent condensation of gases, or vaporize liquids prior to analysis. For example, a temperature-controlled pressure regulator may be used to preheat liquids prevent condensation of gases, or vaporize liquids prior to analysis (e.g. chromatographic analysis).
Temperature-controlled pressure regulators typically employ steam or electric heating to control the temperature of a process fluid. The process fluid is heated within the regulator because the process fluid experiences a substantial decrease or drop in pressure through the regulator (e.g., across a valve seat). The decrease in pressure causes a significant loss of heat (e.g., a temperature drop) in the process fluid (e.g., a gas) in accordance with the Joule-Thomson effect. A temperature-controlled regulator applies heat at the point of the pressure drop to increase or maintain the temperature of the process fluid, thereby preventing condensation of the process fluid (e.g., a saturated gas) as the pressure of the process fluid decreases across the regulator. In other instances, for example, it may be desirable for a liquid to be vaporized. In this instance, the temperature-controlled regulator applies heat to vaporize the liquid as the liquid passes through the regulator to facilitate, for example, analysis of the liquid via a vapor sample.
Because of the different applications, a temperature-controlled regulator could be referred to as a heated regulator. For examples a heated regulator may be used to heat (e.g., via a heating medium) an inlet process fluid containing liquid to be analyzed (e.g., a liquid containing hydrocarbons). In another example, a temperature-controlled regulator may be used to vaporize (e.g., via a heat source) an inlet process fluid containing a vapor to be analyzed (e.g., a vapor containing hydrocarbons).